A common type of thermionic converter of a nuclear reactor includes a housing with a hollow collector, and an emitter containing nuclear fuel within the collector. The emitter has one end fixed to the collector and a second or "free" end lying within but out of contact with the collector. The "free" end of the emitter must be supported against sideward movement against the collector while allowing it to move axially as it expands and contracts with changing temperatures. The space between emitter and collector is filled with a cesium plasma in the normal mode of operation of common thermionic converters.
One prior type of support arrangement for the "free" end of the emitter, includes a spring structure formed by a pair of Belleville washers. A forward end of the spring structure lies against the "free" end of the emitter and a opposite rear end lies against a support structure that is supported on the housing. The support structure was formed of ceramic. In tests it was found that as a result of extended exposure to high temperatures, nuclear radiation, and the cesium plasma environment, the ceramic support structure cracked, discolored at its outside edge, and apparently disappeared in the center. These phenomena raise concern over contamination of the space between the emitter and collector by loose ceramic particles, as well as shorting of the cell by the unsupported emitter second end touching the collector. A support arrangement which avoided these problems would be of considerable value.